Rich,
Thanks. I remember your earlier post on the topic but it did not distinguish the QC function vs. statistical process (defect) control testing of the front end processing. There is a difference.
Since each cell is hooked up individually ... they monitor each cell as it goes through the initial charging process (the 'formation charge,' A failed cell is individually flagged at this point.
My question was: Does yield refer to this step?
When the cells are then put in the quarantine chamber (for a nominal 2-week holding period, ... they are not individually monitored ...Whether they check each cell for charge retention or not, at the end of this holding period and prior to shipping, is a good question to ask at the SM. It certainly seems possible to implement a cell-by-cell test at this step, ...
This needs to be clarified.
The most sensitive part of the process is the 'recipe' at the front end, and the thin-film coatings, and this is where statistical sampling of materials for microscopic inspection for material defects, etc is the best that can be done.
This is where the yield does not make sense, without a definition.
Once an individual bicell is constructed, and electrodes attached, they perform an automated impedance check of each bicell prior to stacking into cells.
This is part of Quality Control that I referred to earlier. Some clarification at the SM will help. They need not reveal the efficiency of their front-end processing. Ram |
